1. Field of the Invention
The present invention relates to a cooling or heating apparatus for a circular housing.
2. Description of the Background
There is currently a widespread need to improve engine outputs. In the aeronautics sector one way of achieving this is to reduce the play between rotor and stator to the minimum, particularly in the region where the free ends of the rotating blades of the rotor meet the housing surfaces facing them. Means to achieve this have already been designed, particularly by varying the diameter of the housing. The commonest procedure consists in imposing thermally-induced dilations or contractions on the outer surface of the housing by blowing gas at the required temperature taken from other sections of the machine in the area opposite the gas exhaust pipe, thereby heating or cooling the housing as required.
It is, however, vital that the temperature of the entire surface of the housing has a high degree of uniformity. A known apparatus consists in fitting two networks of semicircular tubes around the housing such that each network covers one half of the circumference of the housing and is in turn connected to a distribution unit supplied by a pipe connected to each tube of the network at its mid-point. The gas is thus dispersed through the tubes of the network, travelling from the middle of each tube to its end. It leaves the tubes via. apertures directed at the housing. This configuration explains why the tubes are known as "shower collars".
Although it is true that this type of apparatus blows gas more or less uniformly over the entire outer surface of the housing, it nevertheless fails to give it a uniform diameter because the gas heats as it travels through the tubes and may therefore give up more heat on arrival at the ends of the tubes than near to the distributor units. Moreover, the housing gets hotter away from the surfaces near the distributor units and therefore assumes an ovoid shape, the largest diameter of which is located at the surfaces where the network or tubes interconnect.